The present invention relates to a mechanical lumbar support for a seat back. More specifically, the present invention relates to a mechanical lumbar support intended for use in an automotive seat.
Consumer trends have forced automobile manufacturers to provide ever increasing levels of comfort in the products being offered for sale. This includes providing multiple seat adjustment components such as reclining mechanisms, headrest height and tilt adjusters, and variable lumbar support devices. These components are designed to meet the physical needs of various sizes of seat occupants. However, to meet these needs, these comfort components require a high level of complexity due to the number of moving parts necessary to provide support at various locations. In particular, the variable lumbar support devices presently being used have included cables and pulley devices that are threaded throughout the seat back.
The complexity of lumbar support devices of the present art consume a significant amount of packaging space and add a considerable amount of mass to the seat. One such device is disclosed in U.S. Pat. No. 5,567,011 to Sessini. Sessini discloses a lumbar support device that requires a cord be threaded through a seat back and routed with a series of pulleys for both adjusting the height and the magnitude of the lumbar support. While devices such as this fulfill comfort expectations, they are costly to produce and difficult to assemble. Further, this type of device requires that a seat back have considerable thickness to enclose all of the lumbar adjustment components.
Therefore, it would be desirable to design an adjustable lumbar support device that meets the needs of various sizes of seat occupants and yet does not adversely affect mass, cost, or packaging space of the vehicle.
This invention relates to a powered lumbar support device intended for use in an automobile seat back. The device includes a panel that has a first end and a second end and is biased in a forward direction for providing an arch in the seat back. A lumbar frame secures the support device to the seat back. A first gear box has an arching rack and an arching pinion is affixed to the lumbar frame. A first cable connected to one of the panel ends and to the arching rack. A first motor engages the arching pinion for moving the first cable and changing the distance between the first end and the second end. By changing the distance between the first end and the second end, the arch in the panel can be changed for adjusting the amount of lumbar support.
A complaint spring is connected to one of the ends of the panel and to the first cable. The compliant spring includes a contracting spring force that is greater than the extending force generated by the drive mechanism. Therefore, the compliant spring will prevent the control module from sliding upon the lumbar frame. However, when the panel is subjected to enough force to overcome the contracting spring force, the compliant spring stretches increasing the distance between the first end and the second end changing the arch in the panel. The compliance provided to the panel by the resilient spring provides an additional level of comfort to the seat occupant not otherwise available in a rigid lumbar support device.
The first gear box is powered by a small electric motor eliminating the need for cable and pulley devices for changing the amount and the location of the lumbar support in the seat back. Further, the first gear box is packaged into a compact lumbar support module that is easily installed into a seat back frame without having to route cables. Due to the compact nature of the module, lumbar support can be provided in seat backs that are much thinner than those currently in use. Still further, the modules are much less expensive to produce than the current cable and pulley style devices. The low cost provides the ability to install lumbar support devices into economically priced automobiles.